Such vessels, and the term vessel is used here to include also packages and containers of different kinds which normally, at least partially, have walls of a material which depends on the actual kind of heating. If the heating takes place by heat radiation of the type infrared heat radiation from e.g. a cooking plate, the material may be metal, at least in the bottom. If the heating takes place by means of the nowadays very common heating type using micro-waves, then the material may be cardboard or plastics or the like. Below, to facilitate, such vessels, along with the instant content in each case, will sometimes be referred to as "object".
Common to all types of heating is the problem of accurately controlling the temperature, e.g. to prevent that the temperature is insufficient for the application in question or to prevent that the vessel as used bursts up and starts leaking due to too a high internal pressure within the vessel, which may happen if the temperature has unintentionally become too high.
To achieve such a temperature control it is known to provide the vessel with an information carrier having one or more optically readable control information fields which information carrier is adapted to be used in order to indicate the temperature of the object as the object is heated in an oven.
Here, it is conceivable, for instance, to watch visually how the information carrier shifts color as the desired temperature has been reached, so that the heating procedure may be stopped then. However, the information carrier is preferably adapted to cooperate with an optical reading device of the oven and a control device to control the heating procedure at least partially in dependence of the read temperature information. It is preferred that the information carrier is arranged directly on the heating object, e.g. as a disposable label or, alternatively, as a device for repeated use, which device is applied on the object, its vessel, package or contaner, e.g. as the heating is performed.
The information carrier may comprise a field of temperature sensitive color which exhibits a color shift at the desired end temperature of the object, preferably the ready-temperature of a food-stuff or a beverage.
It is conceivable that the information carrier has the shape of a label or a device for use in an oven having a lighting within the oven cavity, in which case the information carrier preferably is characterized in that the field with temperature sensitive color is composed of two layers, namely an uppermost layer, which shifts from transparent into non-transparent, or vice versa, at a color shift, and a lowermost layer, which exhibits fluorescense at activation by the oven cavity lighting.